An important theme throughout the novel is the importance of thinking through problems rather than acting impulsively or irrationally. The core thing that sets Lisa apart from the other children is her realization that she and Todd can think for themselves in order to survive: “It was thinking that kept people alive and that gave them all the wonderful things” (23), she realizes in Chapter 2. From that point forward, she applies her newfound understanding to achieve success both for herself and as a leader of the community: She uses logic and reason to figure out new places to find supplies; she devises new ways to collect and store the supplies in order to keep them safe; she develops a response to the threat of neighborhood gangs; and after she loses Glenbard, she crafts a plan to retake the school. At every step, where other children act impulsively or irrationally in the face of a challenge or threat, Lisa instead thinks through the problem to come up with a longer-term solution rather than a short-term one.

This is probably the most important theme in the novel, as it relates directly to Nelson’s stated purpose: to show children that they can think for themselves.